Almost all wheelchairs include rear wheel locks that prevent the chair from rolling when an occupant either attempts to sit in or rise from the chair. Because the frail physical or mental state of many occupants often prevents them from engaging such locks, many wheelchairs also employ anti-rollback apparatus. Anti-rollback apparatus prevent unintended rearward chair motion when the occupant is either attempting to get in and out of the chair or propel it uphill. Anti-rollback apparatus include clutch and rack and pinion systems such as those described in U.S. Pat. Nos. 6,371,503; 6,347,1088; 6,203,041; and 4,538,825.
There are times, however, when an occupant, in order to best maneuver a wheelchair, needs to be able to move the wheelchair backwards. Entering and exiting a lift is one example of a situation where selective disengagement of an anti-rollback apparatus would be desirable.
It still proves difficult to propel a manually propelled wheelchair up an incline even if the chair is equipped with an anti-rollback device. The occupant must generate sufficient force to propel the combined weight of the occupant plus the chair up the incline by accelerating through rapid rotation of drive wheels using two hands. Not all occupants are strong enough to do so, nor is it safe or convenient for an occupant to occupy both hands solely to propel the chair. Some wheelchair occupants may have lost the use of a hand and therefore are limited in the power they can generate. Even if a occupant is strong enough to propel the wheelchair a substantial distance up an incline, the inherent mechanical disadvantages of current chair designs prevent the efficient translation of linear acceleration force to upward propulsive force along the incline. Thus, the chair may roll backwards, even if equipped with anti-rollback means.
Braking while descending an incline is another problem. Current wheelchair designs rely on wheel-mounted brakes to slow the chair as it descends along an incline, and these too can prove ineffective in slowing the chair to a safe speed. These systems may require an occupant to divert his attention from steering the chair and require him to shift his hand or hands from a steering device to a braking device. The wheelchair is left temporarily uncontrolled during the dangerous descent period.
While motorized wheelchairs solve these problems to an extent, many users cannot afford such chairs. There is therefore the need to provide a means of single handedly propelling, steering and braking a manually propelled wheelchair to afford safe transportation to those who cannot afford or do not have access to motorized wheelchairs. A solution to the aforementioned problems would apply equally to any number of manually propelled vehicles, including carts and toy cars. While occupants of such vehicles may not be handicapped or infirm, they nonetheless might lack the dexterity and strength to propel, brake and steer the vehicle.